Nuclear agencies release information regarding emergency events at nuclear reactors, which indicate a risk to the public, through regular local media. There are four emergency classification levels, according to the United States Nuclear Regulatory Commission (NRC).
Notification of Unusual Event
Events are occurring, or have already occurred, that threaten the level of safety at the site. It is unclear whether radioactive material has been or is being released. Workers are at risk.
Alert
Events may result in a substantial degradation of the level of safety at the site. A release of radioactive material is expected to be limited.
Site Area Emergency
Events will likely result in major failures of plant functions, which are needed for the protection of the public. Radioactive releases are expected to stay within the Environmental Protection Agency (EPA) "protective action guides."
General Emergency
Actual or imminent substantial core damage or melting of reactor fuel and potential loss of containment integrity. Radioactive releases expected to exceed the protective action guides.
